In today's antenna system comprising a transmitting array antenna and a receiving array antenna, there is coupling between the transmitting antenna and the receiving antenna when they are used at the same time. This is a problem since the transmitting antenna could be too “loud” for a receiving antenna. In prior art the problem with coupling have been solved by introduction of physical obstacles such as walls, etc.
Coupling between subarrays in an array antenna may constitute a major problem since a transmitting antenna subarray may make another subarray for receive more or less useless because of interference.
Reduction of the subarray coupling is not an easy task. The large bandwidth of broadband array antennas is a result of strong element coupling.
The possibility to use existing adaptive beam-forming techniques to reduce the coupling is known in far field pattern, but the previously known technique do not reduce the subarray coupling.
The conclusion is that traditional adaptive beam-forming techniques are not appropriate for reduction of subarray coupling.